1. Field of the Invention
The present invention relates generally to construction hardware and a method for reducing the corrosion thereof. More specifically, the present invention relates to construction hardware and the like which have been manufactured from coil steel and a method of applying a coating thereto for reducing corrosion resulting from reaction with chemicals in chemically treated wood.
2. Description of the Prior Art
Construction hardware as used herein refers to various hangers, connectors, straps, tiedowns and the like which are used in the construction industry to connect wooden structural members to one another. Such construction hardware is commonly manufactured from rolls of coil steel. Many applications of such construction hardware are for use in connection with wooden structural members comprised of lumber treated with chemical preservatives (so called “treated lumber”).
Treated lumber is commonly used in outdoor structures exposed to moisture and the environment to reduce deterioration of the lumber. Until a couple of years ago, the most common chemical preservative used for this purpose was a combination of chromium, copper and arsenic, namely chromated-copper-arsentate. This chemical preservative was commonly referred to as “CCA”. For protection against atmospheric and other possible forms of corrosion, it was common throughout the industry to provide construction hardware with a protective coating of zinc or a zinc alloy. Initially, such zinc coating was applied at a thickness of G60 (0.6 oz. per square foot). More recently, to comply with various foreign standards, the zinc coating has been applied at a thickness of G90 (0.9 oz. per square foot). Thus, a G90 coating of zinc was believed to be a sufficient corrosion protector for construction hardware used with CCA treated lumber.
In part, due to the presence of arsenic in the CCA preservative, the wood treatment industry recently made a voluntary decision to eliminate arsenic from the preservative and thus moved away from CCA. The most widely recognized replacement wood preservative is a water based wood preservative commonly referred to as ACQ comprising a combination of copper oxide and a quaternary ammonium compound. While treatment of construction hardware with zinc at a thickness of G90 sufficiently protected CCA coated hardware from atmospheric and other various other forms of corrosion, most test results suggested that ACQ treated lumber added a further form of corrosion to construction hardware via a dissimilar metal reaction between the copper and the zinc. The industry response to this increased corrosiveness was to provide construction hardware with a thicker layer of zinc, namely, G185 (1.85 oz. per square foot). While this increased thickness of zinc functioned to extend the usable life of a piece of construction hardware from the destructive corrosion of ACQ, the thicker zinc coating was still available to react with the copper in the ACQ treated lumber via a dissimilar metal reaction. Thus, increasing the zinc protective layer on the construction hardware still involved a solution comprised of a sacrificial coating material. This necessarily resulted in a limited, but undetermined, useful product life.
Accordingly, there is a need in the art for construction hardware with alternate corrosion reducing properties and alternate methods of reducing corrosion between construction hardware and preservative treated lumber and particularly between construction hardware and ACQ treated lumber.